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THIOCARBANILIDE                     I

changes to reddish-yellow. Dimethylamine is evolved and is
easily recognised by its smell. After cooling, acidify the liquid
in the flask and extract with ether. On distilling off the ether,
nttrosophenot (quinoncoximc) remains in the form of dark-
coloured crystals, which are difficult to purify.

f"  VI   ./   ^(Cri"^   .   IT i   ,}.....p   TY   ,/ O           i   XT T4 / r1 TJ   \
C(}   '>\NO         +    -   """    (5   >}\NOH+    H^H.V2
The presence of a nitroso-compound may he detected as
follows : Melt together a minute quantity of nitrosophcnol and a
few crystals of phenol. Add about 2 c.c. concentrated sulphuric
acid and warm very gently. A blue solution is obtained, which
changes to red on dilution with water, and back to blue on
adding alkali (Liebermann's "nitroso" reaction ; see Reaction,
p. i So). See Appendix, p. 280.
Thiocarbanilide(Diphenylthiourea), CS/^j 11SS;'
\IN rK,ttns
Hofmann, Annalcn, 1849, 70, 14^,
30 grms. aniline.
30           carbon bisulphide*
30           absolute alcohol.
The aniline, carbon bisulphide,1 and alcohol are poured into a
round flask (\ litre), and heated for a day (8 hours) on the water-
bath with upright condenser. As hydrogen sulphide is evolved
the operation must either be conducted in the fume cupboard or
an exit tube must be attached to the top of the condenser tube
dipping into soda-lime. The contents of the flask solidify after
a time. When the. reaction is complete, the condenser is reversed,
and excess of carbon bisulphide and alcohol distilled off on the
water-bath. The residue is washed on to a filter with very dilute
hydrochloric: acid, to remove any unchanged aniline, and then
with water. The crystals are dried on a porous plate, and a por-
tion crystallised from spirit. Yield 30......35 grams.
2C0H{VN H., -i- CS,:;. CS(N HC,.Mf,)2+ HaS
1 C;irbon bisulpliitU- 1>eing very volatile and <:xci;cdin;j;ly inflammable, great care
must be taken when usintf it in the neighbourhood of a ilame.